Are we meat eaters or vegetarians? Part III
A little over two years ago I wrote a couple of posts arguing that we cut our ancestral teeth on meat, and that contrary to all the vegetarian blather about colon length, tooth structure, etc., the archeological and anthropological data convincingly demonstrates we were descended from meat eaters, not vegetarians. (Click here and here for those posts.) A couple of recent developments have now inspired me to write a third.
First, I noticed in both talking with people at the Ancestral Health Symposium last August and attending a number of the talks that many followers of their own version of the ancestral diet are dismayingly including more and more carbohydrates. And recommending more to their followers.
When MD and I wrote Protein Power in the mid 1990s, we used the Paleolithic diet as an argument for the efficacy of the low-carb diet. If pre-agricultural man evolved in a milieu devoid of carbohydrate-dense foods, we posited, then natural selection should have culled those who didn’t thrive on such fare, leaving us, the descendants, powered by metabolic processes that performed better on protein and fat substrates. If the rampant obesity and diabetes (we just thought it was rampant then) was a consequence of a diet we weren’t designed for, then switching to one that better suited us metabolically should produce substantial changes to the good. Which it undeniably does.
I can’t help but recall the great quote by Dr. Blake Donaldson, who changed the complexion of his practice in New York after spending some time with Vilhjalmur Stefansson. Wrote Dr. Donaldson in Strong Medicine, his book about an almost all meat diet:
During the millions of years that our ancestors lived by hunting, every weakling who could not maintain perfect health on fresh meat and water was bred out.
Now, it seems, many who have taken to the Paleo diet have started to drift from the Paleo-is-basically-low-carb paradigm into the Paleo-is-anything-that-isn’t-Neolithic paradigm. And although Neolithic man grew all sorts of crops, most Paleo dieters consider only grains to be truly Neolithic foods. Some Paleo dieters take it a step further and argue that since pre-agricultural man couldn’t have domesticated animals (other than perhaps canids of some sort), then he couldn’t have eaten dairy products. So, those Paleo purists avoid grain and dairy products. Both the dairy and non-dairy Paleo dieters, however, are starting to include larger amounts of carbohydrates – primarily starch – into their diets on the presumption that Paleo man would have eaten it.
I have no doubt that Paleo man would have been face down in a box of donuts had he been given the opportunity. But he wasn’t. Nor was he often presented with the opportunity to indulge in a carb fest composed of high-starch fruits and vegetables. Maybe in the fall when the fruit ripened (if he could beat the birds and bugs to it), but not much of a chance during the rest of the year.
(I am aware that Denise Minger put up a post not too long ago showing all the high-starch, high-sugar tropical fruits available in tropical areas, intimating that early man must have consumed these and, therefore, should have evolved to do okay on high-carb diets. Problem with this reasoning is that archaic homo sapiens migrated out of tropical areas anywhere from 60,000 to 150,000 years ago and went through the crucible of natural selection in other less fruit-laden climes. People of European descent certainly had ancestors who could not avail themselves of tropical fruits at any time.)
The second event driving me to write is a line out of a guest post on Richard Nikoley’s Free the Animal blog by Darrin Carlson titled “The Five Failings of Paleo.” In Mr. Carlson’s own words, here is Paleo Fail #1:
We Don’t REALLY Know What Our Ancestors Ate. [Bold and caps in the original.]
I disagree for a couple of reasons. First, we can be pretty certain what our European ancestors didn’t eat. They didn’t eat dwarf wheat, Red Delicious apples, bananas, Bartlett pears or any other hybridized or tropical fruits commonly available today. As far as we know, there were no Paleo Luther Burbanks grafting and hybridizing plants to make them bigger and sweeter. Our predecessors would have eaten whatever plant foods were at hand, which is pretty much what you still find if you go out in the woods today. They would have had to battle the birds and other wildlife to get to these fruits, and would have had them available only seasonally.
The second reason I disagree is alluded to in a way by Mr. Carlson in his explanation of Fail #1: Said he:
We have yet to find a magic phone booth that will transfer us back through time–Bill and Ted notwithstanding–to directly observe how our great-times-450-grandparents lived.
Actually we do have such a ‘magic phone booth’ available to us, or at least to those of us who know how to use it. It’s an isotope ratio mass spectrometer, and its use has been refined over the past 30-40 years to allow us to peer back in time and calculate what our ancestors ate.
I learned about this ‘magic phone booth’ in the fall of 2000 in Hamburg, Germany where MD and I attended a great conference titled Meat and Nutrition. After the last talk, on a cold, dreary, foggy, drizzly afternoon, MD, Loren Cordain and I lit out to make a pilgrimage to Indra and the Kaiserkeller, the dives where the Beatles had gotten their start in the early 1960s. We asked Michael Richards, a professor at the University of Bradford to join us. On the first morning of the meeting, Michael had given a riveting talk on the use of stable isotopes to determine the diet of early man, and I wanted to find out more.
After roaming the Beatles’ early haunts, we decamped to a Hamburg coffee house to get warm. I asked many questions about the stable isotope methodology and have followed the growing literature on it since. Michael has turned into an academic superstar and is now at the prestigious Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, where he continues to publish his work on the isotopic analysis of the diet of early man.
Let’s take a look at the ‘magic phone booth’ of stable isotope analysis and see what it shows. The whole notion is fairly complex so I’m torn between making its science simple enough for Homer Simpson to understand, which really doesn’t do the technique justice, or making it unnecessarily difficult. I’m shooting for something in between.
As most everyone knows, atoms are composed of protons, electrons and neutrons. The number of protons gives an element its atomic number. A given element always has the same number of protons but can have varying numbers of neutrons. Carbon, for example, has six protons (and an atomic number of 6). But the carbon atom can have 6, 7 or 8 neutrons. All three versions are still carbon, but the atoms vary by the number of neutrons. These different versions are called isotopes, so basically isotopes are atoms of the same element with the same number of protons but differing numbers of neutrons. The atomic mass of an atom is determined by the number of protons and neutrons it contains, so although carbon always carries the atomic number of 6, carbon has three different atomic masses: 12C, 13C and 14C.
Carbons with an atomic mass of 12 and 13 (12C, 13C) are stable whereas 14C (pronounced carbon 14) disintegrates radioactively over time. This radioactive decay is what allows scientists to determine the age of organic materials up to about 40,000 years old. The discovery of natural radioactivity of 14C and its usefulness in determining age garnered Willard Libby the 1960 Nobel Prize in Chemistry. Although the unstable isotopes such as 14C have their uses, we are concerned here with the stable isotopes. Primarily 12C and 13C and 14N and 15N (nitrogen 14 and 15). From these four stable isotopes, we can learn a lot about the diet of early man.
Nuclear weapons started adding 14C into the atmosphere in the mid 1900s, so the average ratio of 12C, 13C and 14C have change slightly. Since 12C and 13C are stable, there has been virtually no change in the ratio between them over time. But the ratio of the two has been found to differ from one carbon-containing material to another. For instance, carbon dioxide generated from marine limestone contains more 13C than does carbon dioxide generated from burning wood. In general, marine sources have greater amounts of 13C than do terrestrial sources.
Just to make it a little more complex, when researchers run samples through a mass spectrometer to determine the 13C/12C ratio, this ratio is compared to an agreed standard. Then the difference between the sample and the standard is called the relative 13C content, which is designated by ?13C and measured in parts per thousand. (‰) So if the sample has a ratio less than the standard by 5 parts per thousand, it is defined as having a ?13C value of ?5‰.
Don’t worry about all the above – just remember when you see ?13C from now on, it refers to the ratio of 13C to 12C. Don’t despair. It will be easier as we go along.
Of the dry weight of bone, a little over 25 percent is collagen, and it is collagen that is the tissue of choice for stable isotope analysis. Virtually all of the carbon and nitrogen in collagen comes from protein, and since most protein in the human body ultimately comes from protein in the diet, the carbon and nitrogen isotopes in the collagen reflect the protein sources in the diet. And since the stable isotope composition of collagen turns over very slowly, the ratios of carbon and nitrogen stable isotopes reflect diet over about an eight to ten year period.
Stable isotopes of both carbon and nitrogen occur in varying proportions in different foods, and these proportions are passed along to the animals, including humans, that ate these foods. By knowing the proportions of the stable isotopes in various foods, we can determine which of these foods contributed to the diet of the animal in question by analyzing the stable isotopes in its collagen.
Researchers are able to extract valuable data from the collagen of ancient bones. Unfortunately ancient bones are not thick on the ground, and since a part of the bone has to be destroyed to perform the stable isotope analysis, these analyses are not done by the thousands. Each time a skeleton or group of skeletons is unearthed, Michael Richards and other stable isotope researchers try to snare a little piece of bone and go at it with the mass spectrometer. This kind of work has been done for several decades now, and the results – though painstakingly obtained one specimen at a time – are accumulating, and there is now a fairly substantial body of data. And this data is remarkably uniform in what it shows of the dietary habits of our ancient European ancestors.
The ?13C and ?15N figures reveal different information about the diet of Paleo man. Since the 13C isotope is found in greater quantities in the marine environment than in the terrestrial, a large ?13C indicates a diet higher in seafood protein whereas a lower?13C is associated with a diet composed primarily of protein foods from the land. Researchers have accumulated considerable data on the?13C of seals and other such animals that spend their lives in the oceans consuming other marine life to compare with the data gleaned from bones of animals living on the land far from the sea. By noting how the ?13C from ancient human bone compares to these extremes determines whether the human dined on protein from terrestrial or marine sources of from a combination of the two.
The ?15N tells a different story.?15N basically tells us where an animal or human is on the food chain. Basic plant foods maintain a fairly constant ?15N value. When animals, typically herbivores, eat these plant foods, the stable N isotope in the plant food tends to concentrate by anywhere from 5-8 percent in the collagen of the animal. So if the collagen of an animal is found to have, say, a 7 percent greater ?15N than the local flora, one can say the animal was an herbivore. Animals that are known herbivores, when analyzed, fit this spectrum.
Any animal, including man, that dines on herbivores will have collagen sporting a ?15N that is about 7 percent greater than that found in the herbivores that are the meal, a fact confirmed by stable isotope analysis of known carnivores. A super carnivore (for lack of a better name) that dines on other carnivores and herbivores would have an even greater ?15N level.
So, ?15N pinpoints us on the food chain while ?13C tells us whether the protein we eat is surf or turf or both.
Now that we have a full understanding of the ‘magic phone booth’ of stable isotope analysis, let’s take a look at what the data show.
The data taken as a whole show the following:
Early man was a high-level carnivore. (As was his distant relative the Neanderthal, who lived contemporaneously with ancient man in Europe.) A higher-level carnivore, in fact, than foxes, wolves and other known carnivores. The earliest anatomically modern humans got most of their protein from animals of terrestrial origin. As time passed and the populations of large game thinned due to heavy hunting by both humans and Neanderthals, the human position on the food chain didn’t change, but sources of protein changed from all terrestrial to more and more marine (which includes fresh water fish, mussels, clams, etc., all of which have a similar? 13C as animals from the ocean). Irrespective of whether the protein came from the land or the sea, early man occupied a super-carnivore niche in pre-agricultural days.
Here are a couple of graphics of stable isotope studies done by Michael Richards – one on Neanderthals; the other on early modern man – I presented at the Ancestral Health Symposium back in August at UCLA.
As you can see from this slide, the Neanderthal subjects were ranked a bit above the wolf and fox on the predator/meat eating scale. As Michael Richards commented in the paper cited above:
…the European Neanderthal diet indicates that although physiologically they were presumably omnivores, they behaved as carnivores, with animal protein being the main source of dietary protein.
When we take a look at another study evaluating ancient humans, we see much the same thing.
As compared to the Arctic fox, you can see that early humans were way off the chart to the right. Michael Richard’s commentary:
We were testing the hypothesis that these humans had a mainly hunting economy, and therefore a diet high in animal protein. We found this to be the case…
The bulk of the stable isotope studies show both Neanderthals and ancient humans were, at their robust cores, meat eaters to the max. What the stable isotope studies don’t show, is how much carbohydrate these folks ate along with their meat. (Actually some stable isotope studies do show what kind of carbs in the sense that they can differentiate between grains and non-grains, but since there were no grains in Paleo times, that isn’t a concern.) But since we do know that wolves and foxes are predators that consume mainly food of animal origin, and we know that early humans have an even more carnivorous stable isotope footprint, it seems unlikely that these humans would have consumed many calories from non-animal sources. Remember, natural sources of protein are virtually always associated with fat (copious amounts of fat if the protein is from large game and the entire carcass is consumed), so it’s doubtful there would be either the capacity or the necessity for complementing the basic diet of fat and protein with much carbohydrate. But, nonetheless, even if our ancient ancestors did eat some carbs they could scrounge while in season, the stable isotope evidence clearly demonstrates they were not vegetarians.
If you would like to read more about stable isotope analysis for determination of the diet of early man, a good place to start is with the publications of Michael Richards.
Other good sources for basic information:
Katzenburg MA (2008) Stable isotope analysis: a tool for studying past diet, demography, and life history. In Katzenburg MA, Saunders SR (eds) Biological Anthropology of the Human Skeleton. (Hoboken, Wiley-Liss) 2nd Edition pp 413-441
Schoeninger MJ, DeNiro M (1984) Nitrogen and carbon isotopic composition of bone collagen from marine and terrestrial animals. Geochim Cosmochim Acta 48:635-639.
Schoeninger MJ (1995) Stable isotope studies in human evolution. Evolutionary Anthropology 4(3): 83-98.
van der Merwe, NJ (1982) Carbon isotopes, photosynthesis, and archeology. American Scientist 70: 596-606.